During the oil and gas exploitation and transportation processes, CO2 is usually present in oil gas as a component of natural gas or oil field gas, or the appearance of other oil recovery techniques, such as CO2 flooding oil recovery technique, air flooding or other oil recovery techniques, produces considerable CO2, such that the metallic conduit and device suffer from severe carbon dioxide corrosion during the exploitation of oil and gas fields, which causes a shortened life span of the device and deterioration of material property, and may easily cause a huge financial loss for the oil and gas fields. In addition, the corrosion will also cause casualties and severe environmental pollution.
The enhancement of the research on corrosion and protection may bring about a tremendous economic benefit for petroleum industry. At present, the protection from carbon dioxide corrosion in the oil and gas fields in our country is generally achieved by the following four methods: selecting an alloy steel with better corrosion resistance, cathodic protection technique, surface coating and injecting corrosion inhibitor. As indicated by the practical experience at home and abroad, among the four types of corrosion control techniques, the method of injecting corrosion inhibitor, as compared with the other protection means, has become a most widely used and practical method in the protection from carbon dioxide corrosion in the oil and gas fields because of numerous advantages including: the disposing process is simple, and is easy to implement; the economic cost is relatively low; and the method can protect all of the materials constituting the device, without the need of additional investment for adding anticorrosive devices (e.g., cathodic protection system).
As to CO2 corrosion in a medium of oil field water with a temperature below 100° C., many work and researches have been done at home and abroad, and many efficient corrosion inhibitors have appeared. However, under the condition of a high temperature up to 150-250° C., most of the existing corrosion inhibitors are inactivated and thus are unable to play a corrosion-inhibiting role.